It is well known and understood in the vehicle safety industry that knowing the vehicle's lateral velocity just prior to a side impact or a rollover event can greatly improve the performance of the vehicle's occupant restraint system by allowing faster and more robust deployment decisions.
Many present-day vehicles are equipped with electronic vehicle stability systems. These systems consist of various sensors including low-range lateral and longitudinal accelerometers, yaw rate sensors, steering angle sensor, and wheel speed sensors. Using physical principals and models, the vehicle's lateral velocity may be calculated from these sensors. This information may be used by the crash sensing system to enhance performance during side impact and rollover crash events. Sensing systems that use these methods will have good performance in real-world crash situations.
However, in a controlled test situation the sensors that are needed to calculate the vehicle's lateral velocity do not experience the physical forces that normally precede the crash event. For example, if a vehicle is being pulled sideways into an object, then there will be no yaw rate, no wheel speeds, and no steering angle. The only sensor that will experience any physical indication that the vehicle is moving is the lateral accelerometer. In theory, the lateral velocity can be calculated by simply integrating the lateral acceleration. However, the state-of the-art accelerometers are not perfect sensing devices. They are prone to offset drifts and shifts that are within the same range as the pulling force used to accelerate the vehicle towards the impact object. Therefore, the performance of the vehicle's sensing system will not be as good during a crash test as it would be in the real world unless a special test set-up is used to artificially inject the lateral velocity or inject the sensor signals needed to calculate it.
Presently, special test set-ups are not allowed for federally mandated tests. The method described herein allows the vehicle sensor system to calculate and use lateral velocity during controlled crash tests without any special test set-up.